<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    //定义常量
    const username='Rose'
    //会报错：常量不能更换引用
    // username='Jack';

    console.log(username)
</script>
</html>